Annealing molecular beam epitaxy grown Ge/Si(100) islands spontaneously for
ms quantum dot molecules and rings. Quantum dot molecules (QDM) are close-p
acked arrays of several SiGe alloy hut clusters arranged with rectangular o
r circular symmetry. Rings are 3D structures with a depressed center. Both
of these structures are related to island ensemble coarsening. Si interdiff
usion into the perimeter of nominally pure Ge dome clusters forms a Si-rich
annulus surrounding a Ge rich core. This lower melting point core diffuses
away during coarsening of the island ensemble leaving behind the QDM. Larg
e ring structures are formed by rapid coarsening of large, dislocated clust
ers during high temperature anneals. (C) 2001 American Institute of Physics
.